bash-script

name	bash-script
description	Generates production Bash scripts with a visual timeline UI, state-based interactive prompts, and strict error handling. Use when asked to write a bash script, create a shell script, or build a DevOps or CLI script with framed terminal output.

Bash script

Generate production-ready Bash scripts for DevOps and CLI workflows. Enforce strict formatting with a visual timeline UI and state-based interactivity.

Load ${CLAUDE_SKILL_DIR}/references/patterns.md for the timeline lifecycle, logging, interactive prompt, help-screen, and full-script code templates. ${CLAUDE_SKILL_DIR} expands to this skill's own directory, so the path resolves from any project. Copy those definitions verbatim, keeping only the colors and functions the script actually uses.

Script setup

• Start with #!/usr/bin/env bash, set -e, and set -o pipefail.
• Bash 4+ features (namerefs, associative arrays) are allowed.
• Implement a visual help screen via show_help if the script accepts arguments.
• Do not rely on unset variables. Use ${VAR:-default}.

Visual timeline

• Maintain a vertical timeline (│) from ┌ to └ throughout all output.
• Write all frame output (┌, │, ├, └, log lines, prompts) to stderr via >&2. Write data (JSON, lists, piped values) to stdout. --help is the exception and prints to stdout.
• Open the timeline once at the start of main() via open_timeline "Title", before any logic, prompts, or checks.
• Close the timeline via trap close_timeline EXIT, registered immediately after open_timeline.
• On success, disable with trap - EXIT, then print └\n and the success message manually.
• On cancellation and error, never print └ manually. The trap owns those exits.
• Use state transitions for interactive prompts: ◆ active, ◇ inactive.
• Do not add diamonds (◆ or ◇) to non-interactive log functions.
• On cancellation, show ◇ ... Cancelled, exit 1, and make no log_error call. Both ask() and select_option() handle escape cancellation identically.
• Guard interactive prompts against non-TTY stdin with [ -t 0 ] and render a framed log_error when a TTY is required but absent. Never let read block silently on piped input.

Code style

• Decompose by responsibility: each function does one thing, main() orchestrates only.
• Name functions verb-first: validate_input, deploy_service, install_dependencies.
• Do not use global variables except exports from ask().
• Do not define unused color variables.
• Do not include comments except the shebang line.
• Use sentence case for section headers and log messages. Proper nouns and product names retain their casing.
• Quote variables inside parameter expansions: "${file#"$dir"/}" not "${file#$dir/}".
• Quote variables in test brackets: [ "$i" -eq "$cur" ] not [ $i -eq $cur ].
• Guard commands that return non-zero on valid empty results: grep ... || true, diff ... || true.

Output hygiene

• Show external tool output by default (git, npm, gh).
• Include context in error messages: log_error "npm install failed: check package.json".
• Do not echo command names before running them. Output speaks for itself.
• Do not log "Starting..." and "Finished..." around every action.
• Do not log intermediate variable assignments.
• Use log_add for item writes (files created, entries added, keys written).
• Use log_info for status confirmations only ("up to date", "check passed").
• Use log_warn for drift, skipped states, or recoverable issues.
• Never use log_info for file or entry writes.

Icon usage

Interactive prompts only:

• ◆ (green): active user input required
• ◇ (grey): completed input, transition via \r\033[K to rewrite the ◆ line in place
• ❯ (green): selected option in a menu
• plain text (grey): unselected option in a menu

Non-interactive logs:

• ├ section branch (log_step)
• ✓ (green): success (log_info)
• ! (yellow): warning (log_warn)
• ✗ (red): error (log_error)
• + (green): add item (log_add)
• - (red): remove item (log_rem)

Validation

Before responding, verify:

• File starts with #!/usr/bin/env bash, set -e, set -o pipefail and uses exactly 2 spaces for indentation.
• Timeline opens via open_timeline "Title", which writes ┌ and │ Title to stderr.
• Timeline closes via trap close_timeline EXIT registered immediately after open_timeline. Success paths use trap - EXIT then manual └\n (to stderr) then the success message. Cancellation and error paths never print └ manually.
• open_timeline and close_timeline are defined and write to stderr via >&2.
• All frame output (│, ├, └, log lines, interactive prompts) writes to stderr via >&2. Stdout carries data only. --help is the exception.
• Interactive prompts (ask, select_option) guard with [ -t 0 ] and call log_error if stdin is not a TTY.
• The timeline (│) appears in all log functions, and interactive prompts use ◆ → ◇ transitions.
• ask() uses \r\033[K to rewrite the ◆ line in place, with no \033[1A cursor-up sequences.
• ask() drains trailing escape bytes with read -rsn2 -t 0.001 _ || true before cancelling.
• All log messages use sentence case (proper nouns and product names exempt).
• Only defined color variables are used in the script.
• Cancellation shows a single ◇ ... Cancelled line without a subsequent log_error.
• Escape key in ask() triggers ◇ ... Cancelled and exits, consistent with select_option().
• Functions follow single responsibility: each does one thing, main() delegates to helpers.
• Logging is concise: no "Starting.../Finished..." bloat, no intermediate variable logging.
• log_add is used for all file, entry, and key writes.
• log_info is used for status confirmations only, not writes.
• Every section header uses log_step, including the first one after the title block.
• File ends with exactly one empty line.